Hi everyone, I got this old Honda VFR 750 from 1986.
It’s a 4 cylinders bike with Keihin VD carbs of 34, V shaped engine.

I’ve cleaned my carburetors, replaced all the 4 intake mainfolds, replaced my idle jet with a compatible one, replaced mixture screw and overflow screw and all their o-rings, replaced also o-rings around the pipes.
Is always the same story: initially, it starts wonderfully, then the rpms begin to decrease gradually and eventually shutting off completely and making it impossible to restart.

When the bike stalls, there are always at least 2 cylinders emitting a lot of white smoke while the other two do not, but I noticed that they changed last time I mounted the carbs (last time was cylinder #1 and #4, now #3 and 4#).

What could it be in your opinion?

I assured that fuel doesn’t come out from the needle while idling, so I don’t think it could be a overfilling problem (maybe?).
I set the float height at 7mm like service manual reports and replaced the needle valve.
Mixture screw set at 2 and 1/2 turns (always read it on the manual)

  • Prestigious-River686OPBEnglish
    1·
    1 year ago

    I didn’t pay attention to the vacuum slides actually, gonna listen carefully next time I’ll be able to restart the bike, it takes a bit of time after it stalls like this, maybe too much flooded, don’t know. What sound do I have to look for, precisely?

    Yes, carburetors cleaned with compressed air and wd-40 with every screws removed, and air comes out flawlessly.

    I don’t get what you mean by “still sound”, but yes, the pilot screws have all their components (spring, washers and oring in this order)

    About carbs fully seated I guess so, but could it be that cylinder #4 and #3 are not properly tightened and could this cause the white smoke issue?

    Thanks for the reply, by the way